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Enanta Announces Japanese Ministry of Health, Labour and Welfare Grants Priority Review for AbbVie’s Investigational HCV Regimen of Glecaprevir/Pibrentasvir (G/P) for the Treatment of All Major Genotypes of Chronic Hepatitis C

If approved, G/P may provide a shorter, eight-week, once-daily,
ribavirin-free cure* for the majority of the patients living with
hepatitis C in Japan1

Glecaprevir is Enanta’s second protease inhibitor being developed
through its collaboration with AbbVie and is one of the two new
direct-acting antivirals (DAAs) in G/P

WATERTOWN, Mass.--(BUSINESS WIRE)--Mar. 14, 2017--
Enanta Pharmaceuticals, Inc. (NASDAQ:ENTA), a research and
development-focused biotechnology company dedicated to creating small
molecule drugs for viral infections and liver diseases, today announced
that priority review has been granted by the Japanese Ministry of
Health, Labour and Welfare (MHLW) to AbbVie for its investigational,
pan-genotypic, ribavirin-free combination of glecaprevir/pibrentasvir
(G/P) for the treatment of all major genotypes (GT1-6) of chronic
hepatitis C virus (HCV) infection. The NDA for the G/P regimen in Japan
was submitted in February 2017.

“Receiving priority review in the U.S., the E.U. and now Japan validates
that there is continued unmet need for patients with HCV around the
world,” commented Jay R. Luly, Ph.D., President and Chief Executive
Officer, Enanta. “If G/P is approved, we look forward to this important
treatment option being available to the estimated 1 million people in
Japan living with HCV.”

The Japanese MHLW designates priority review to certain medicines based
on the clinical usefulness of the treatment and severity of the disease.
Japan has one of the highest rates of hepatitis C infection in the
industrialized world, with approximately 1 million people living with
the disease, 99 percent of whom are infected with genotype 1 (GT1) or
genotype 2 (GT2).1,2 If approved, G/P may provide a shorter,
eight-week treatment duration for GT1 and GT2 patients without
cirrhosis, who make up the majority of HCV patients, and an additional
treatment option for patients with any of genotypes 3-6. G/P is also
intended to address the needs of patients with specific treatment
challenges, including those with severe chronic kidney disease (CKD) and
those not cured with previous DAA treatment.

The New Drug Application (NDA) in Japan is supported by data from the
Phase 3 CERTAIN studies in Japanese patients and supplemented with
registrational studies in AbbVie’s G/P global clinical development
program, which evaluated more than 2,300 patients in 27 countries across
all major HCV genotypes and several special populations. Patient
populations studied included GT1-6, those new to treatment and the
treatment-experienced, those with compensated cirrhosis and without
cirrhosis, and patients with specific treatment challenges, including
those with severe CKD, and those not cured with a prior DAA-containing
regimen. The global program was designed to investigate a faster path to
virologic cure* for all major HCV genotypes (GT1-6) and with the goal of
addressing areas of continued unmet need.

*Patients with a sustained virologic response at 12 weeks
post-treatment (SVR12) are considered cured of hepatitis C.

About AbbVie’s G/P Clinical Development Program

AbbVie’s glecaprevir/pibrentasvir (G/P) global clinical development
program was designed to investigate a faster path to virologic cure* for
all major HCV genotypes (GT1-6) and with the goal of addressing
treatment areas of continued unmet need. In Japan, AbbVie studied the
G/P regimen in additional dedicated clinical trials due to patient and
viral characteristics specific to the Japanese HCV patient population.

G/P is an investigational, pan-genotypic regimen that is being evaluated
as a potential cure in 8 weeks for HCV patients without cirrhosis and
who are new to treatment with direct-acting antivirals (DAA), who make
up the majority of HCV patients. AbbVie is also studying G/P in patients
with specific treatment challenges, such as patients with genotype 3
HCV, patients who were not cured with previous DAA treatment and those
with chronic kidney disease, including patients on dialysis.

G/P is an investigational, once-daily regimen that combines two distinct
antiviral agents in a fixed-dose combination of glecaprevir (300mg), an
NS3/4A protease inhibitor, and pibrentasvir (120mg), an NS5A inhibitor.
G/P is dosed once-daily as three oral tablets.

G/P is an investigational product and its safety and efficacy have not
been established in Japan.

About Enanta

Enanta Pharmaceuticals is a research and development-focused
biotechnology company that uses its robust chemistry-driven approach and
drug discovery capabilities to create small molecule drugs for viral
infections and liver diseases. Enanta’s research and development efforts
are currently focused on the following disease targets: non-alcoholic
steatohepatitis (NASH)/ primary biliary cholangitis (PBC), respiratory
syncytial virus (RSV) and hepatitis B virus (HBV).

Enanta has discovered novel protease inhibitors for use against the
hepatitis C virus (HCV). These protease inhibitors, developed through
Enanta’s collaboration with AbbVie, include paritaprevir, currently
marketed in AbbVie’s HCV regimens, and glecaprevir (ABT-493), Enanta’s
second protease inhibitor product, which AbbVie is developing as part of
its investigational HCV regimen of glecaprevir/pibrentasvir (G/P) now in
registration in the U.S., the E.U. and Japan. Royalties and any further
milestone payments from this collaboration will provide funding for
Enanta’s earlier development programs, including its Phase 1 FXR agonist
program for NASH/PBC, and its preclinical programs for HBV and RSV.
Please visit www.enanta.com
for more information on Enanta’s programs and pipeline.

FORWARD LOOKING STATEMENTS DISCLAIMER

This press release contains forward-looking statements, including
statements with respect to the prospects for AbbVie’s G/P regimen for
HCV. Statements that are not historical facts are based on management’s
current expectations, estimates, forecasts and projections about
Enanta’s business and the industry in which it operates and management’s
beliefs and assumptions. The statements contained in this release are
not guarantees of future performance and involve certain risks,
uncertainties and assumptions, which are difficult to predict.
Therefore, actual outcomes and results may differ materially from what
is expressed in such forward-looking statements. Important factors and
risks that may affect actual results include: the efforts of AbbVie (our
collaborator developing glecaprevir) to obtain regulatory approvals of
its glecaprevir/pibrentasvir (G/P) combination and commercialize it
successfully; the regulatory and marketing efforts of others with
respect to competitive treatment regimens for HCV; regulatory and
reimbursement actions affecting G/P, any competitive regimen, or both;
the need to obtain and maintain patent protection for glecaprevir and
avoid potential infringement of the intellectual property rights of
others; and other risk factors described or referred to in “Risk
Factors” in Enanta’s most recent Form 10-K for the fiscal year ended
September 30, 2016 and other periodic reports filed more recently with
the Securities and Exchange Commission. Enanta cautions investors not to
place undue reliance on the forward-looking statements contained in this
release. These statements speak only as of the date of this release, and
Enanta undertakes no obligation to update or revise these statements,
except as may be required by law.